NF-κB p50 and p52 Expression Is Not Required for RANK-Expressing Osteoclast Progenitor Formation but Is Essential for RANK- and Cytokine-Mediated Osteoclastogenesis

Authors

  • Lianping Xing,

    1. Department of Pathology and Laboratory Medicine, University of Rochester Medical Center, Rochester, New York, USA
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  • Timothy P. Bushnell,

    1. Department of Hematology/Oncology, University of Rochester Medical Center, Rochester, New York, USA
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  • Louise Carlson,

    1. Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
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  • Zhenxing Tai,

    1. Department of Pathology and Laboratory Medicine, University of Rochester Medical Center, Rochester, New York, USA
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  • Mehrdad Tondravi,

    1. National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland, USA
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  • Ulrich Siebenlist,

    1. Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
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  • Fay Young,

    1. Department of Hematology/Oncology, University of Rochester Medical Center, Rochester, New York, USA
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  • Brendan F. Boyce M.D.

    Corresponding author
    1. Department of Pathology and Laboratory Medicine, University of Rochester Medical Center, Rochester, New York, USA
    • Department of Pathology and Laboratory Medicine, University of Rochester Medical Center, 601 Elmwood Avenue, Box 626, Rochester, NY 14642, USA
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  • The authors have no conflict of interest.

Abstract

Expression of RANKL by stromal cells and of RANK and both NF-κB p50 and p52 by osteoclast precursors is essential for osteoclast formation. To examine further the role of RANKL, RANK, and NF-κB signaling in this process, we used NF-κB p50−/−;p52−/− double knockout (dKO) and wild-type (WT) mice. Osteoclasts formed in cocultures of WT osteoblasts with splenocytes from WT mice but not from dKO mice, a finding unchanged by addition of RANKL and macrophage colony-stimulating factor (M-CSF). NF-κB dKO splenocytes formed more colony-forming unit granulocyte macrophage (CFU-GM) colonies than WT cells, but no osteoclasts were formed from dKO CFU-GM colonies. RANKL increased the number of CFU-GM colonies twofold in WT cultures but not in dKO cultures. Fluorescence-activated cell sorting (FACS) analysis of splenocytes from NF-κB dKO mice revealed a two-to threefold increase in the percentage of CD11b (Mac-1) and RANK double-positive cells compared with WT controls. Treatment of NF-κB dKO splenocytes with interleukin (IL)-1, TNF-α, M-CSF, GM-CSF, and IL-6 plus soluble IL-6 receptor did not rescue the osteoclast defect. No increase in apoptosis was observed in cells of the osteoclast lineage in NF-κB dKO or p50−/−;p52+/− (3/4KO) mice. Thus, NF-κB p50 and p52 expression is not required for formation of RANK-expressing osteoclast progenitors but is essential for RANK-expressing osteoclast precursors to differentiate into TRAP+ osteoclasts in response to RANKL and other osteoclastogenic cytokines.

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